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Comprehensive Foot and Pathology Exam Notes (Biopsy, Imaging, Charcot, and Common Pathologies)

Biopsy Techniques and Specimen Handling

  • Importance of careful reading and cross-checking radiology with pathology; pathologist’s readings can be contested in court if the slide isn’t reviewed or if the reading was missed.
  • When you encounter a positive melanoma or similar lesion, always review the slide and discuss findings with a dermatopathologist to understand what was seen and what made it hard to call.
  • Injections and procedures can rapidly change radiographic appearance (e.g., arthritis evolving after an MPJ injection); consider the time course and prior interventions when interpreting images.
  • Punch biopsy basics
    • Punches: commonly 2\,\mathrm{mm} and 3\,\mathrm{mm}; most physicians prefer the punch with a plunger when using a 3\,\mathrm{mm} punch; frequently the plunger aids in removing tissue but not always preferred.
    • In cancer/melanoma cases: punch depth and location matter; punch the proximal matrix to minimize nail plate damage; punching distally increases nail involvement risk.
    • Technique: enter at an angle, punch straight in, and withdraw straight back; ensure the lesion is captured in the bevel for easy grasping with forceps.
    • If the tissue gets stuck inside the skin: do not blow on it. Instead, use a 25\ \text{G} needle to scoop it out; this requires caution to avoid harming tissue.
  • Bleeding control and specimen handling
    • Use a suitable local anesthetic (lidocaine) and be mindful of the ulcer base and tissue inflammation when planning incisional biopsies.
    • For nail-unit biopsies, punch depth and position matter to prevent nail damage; sometimes a true nail-unit biopsy is performed with tissue sent for pathology.
    • When collecting tissue: use a suction-based approach with the 18G syringe; maintain suction to capture cells that may otherwise be left behind; avoid letting fluid flush back onto the floor.
    • Technique variations exist between instructors; some prefer retracting and releasing fluid to push contents forward, then drawing back. Others flush the syringe to avoid losing cells. Learn both, but follow the method taught in your program.
  • Specimen submission and processing (Medicare/lab workflow)
    • Volume of specimen and handling: specimens go into a fixative first (often formalin); tissue must stay in fixative for at least 8\ \text{hours} to ensure proper fixation.
    • After fixation, wash the tissue and then place into a cryoprotective or cryogenic medium (cryovial) for transport; avoid leaving tissue in fixative longer than necessary to prevent degradation.
    • If the lab will pick up the specimen later (e.g., Friday schedule), ensure proper chain-of-custody and labeling so the specimen is preserved until retrieval.
    • Tissue in fixative should not be left for more than 24\ \text{hours} before processing; excessive time in fixative can compromise downstream histology.
    • In many practices, the sample is placed in a fixative, then moved to a cryo or appropriate medium; discuss lab-specific requirements with your pathology department.
  • Practical notes on documentation and consent
    • Always obtain informed consent before biopsy, especially when using biopsies for potential oncologic workup; document consent and rationale in the medical record.
    • When billing and coding, be mindful of the distinction between punch biopsy, incisional biopsy, and excisional biopsy; each has different coding patterns.
    • When handling resources (MA or assistant in the room), ensure proper documentation of who performed the procedure, the depth of biopsy, and the anesthesia used.

Melanoma and Ulcer Biopsies: Clinical Techniques and Decision Points

  • Ulcer base and inflammatory tissue under the ulcer
    • For ulcers, ensure you’re pulling inflammatory tissue at the ulcer base to obtain an adequate sample for pathology.
  • Melanoma biopsy strategy
    • Punch biopsies for melanoma must capture the full depth and margin risk; for nail unit lesions, prioritize proximal matrix sampling to minimize nail dystrophy and to obtain representative tissue.
    • A broad, shallow scoop should be avoided to prevent under-sampling; prefer a narrow and deep approach to capture full thickness and margins.
  • Two-week oncology referral rule (the 2-week rule)
    • Oncology wants patients on the table within 2\ \text{weeks} when cancer is suspected; avoid delaying workup with multiple follow-ups.
    • Delays (e.g., waiting a month for re-evaluation) are discouraged when clinical suspicion for malignancy exists; biopsy timing should be expedited when indicated.
  • Benign vs malignant soft tissue tumors (epidemiology)
    • Benign tumors outnumber malignant ones by a ratio around 15:1 in many settings (the transcript notes “outnumber malignant tumors, a hundred and fifty one” which seems to reference a high benign-to-malignant ratio; interpret as a general rule that malignancies are less common than benign lesions).
    • The incidence of malignant soft tissue tumors is roughly \sim 20\ \text{per million US residents} (as stated in the transcript), underscoring the relative rarity but importance of appropriate evaluation.
  • Imaging and tissue orientation during biopsy
    • When MRI/CT is used prior to excision, ensure the specimen is properly tagged and oriented so the radiology/pathology teams can correlate imaging with histology.
    • If imaging is not annotated with orientation, surgical planning can be delayed or misdirected; proper orientation improves diagnostic yield.
  • Indications for amputation or wide excision
    • Amputation or radical excision is considered with loss of function or when margins cannot be achieved safely without compromising function; the decision depends on tumor type, depth, and anatomic extent.
  • Local anesthesia, instrumentation, and technique notes
    • In biopsy procedures, maintain sterile technique and document anesthesia and any adjuncts (epinephrine use, hemostasis methods).
    • Tools discussed include 18G aspiration needles for tissue removal and a syringe with controlled suction; maintain sterility and proper disposal after use.

Radiology, Pathology, and Clinical Decision-Making in Foot and Ankle Disease

  • Radiology signs of arthritis and degenerative disease
    • Hallmarks on imaging: \text{osteophytes}, \quad \text{asymmetric joint-space narrowing}, \quad \text{subchondral sclerosis}, \quad \text{subchondral cysts (cysts form in nonuniform patterns)}
    • These features predict osteoarthritis and guide treatment planning (conservative measures first; surgery if refractory).
  • Flex sign and Lisfranc considerations
    • In Lisfranc injuries, look for instability patterns on X-ray and consider CT to delineate fracture-dislocation; flex sign refers to visualization of joint instability on imaging.
  • Osteoarthritis management ladder
    • Conservative: NSAIDs, weight modification, custom orthotics, rest, ice, compression, elevation (RICE); injections (corticosteroids, hyaluronic acid in some joints).
    • If conservative measures fail: surgical options vary by joint (fusion for most midfoot and hindfoot joints; replacement may be considered in select joints like the ankle or first MPJ).
  • Stage-based Charcot foot (diabetic neuropathy) and radiographic correlation
    • Charcot foot staging (modified/commonly taught in clinics):
    • Stage 0 (development): clinical signs with no radiographic changes; MRI may show early bone/soft tissue changes.
    • Stage 1 (destruction): destructive changes appear on imaging; clinical signs remain prominent.
    • Stage 2 (coalescence): radiographic signs begin to consolidate; less edema clinically.
    • Stage 3 (remodeling): architectural changes stabilize and remodel; fewer clinical symptoms.
    • The basic idea is to connect clinical signs with imaging changes to guide treatment.
  • Gold standard treatment for Charcot neuroarthropathy
    • Off-loading is central: total contact cast (TCC) is the gold standard for boards and residency exams; CAM boot or custom orthotics may be alternatives when TCC is not feasible.
    • Weight-bearing offloading reduces repetitive pressure and allows healing while preserving limb function.
  • Other classification schemes and their uses
    • Sanders–Fuentes-type schemes (or analogs) used to grade midfoot pathology on radiographs and their correlation with MRI; the two-level (Sanders II) is commonly cited as the midfoot level.
    • The Chantelo classification (as referenced in the transcript) is used to correlate radiographs with MRI findings and to define anatomic levels; for the purpose of this lecture, Sanders II (midfoot) is the most common level discussed.
  • Navicular stress fractures in athletes
    • Navicular stress fractures are common in young athletes (especially lacrosse players in the transcript’s anecdotes) and have a high risk of nonunion due to a watershed area in the navicular’s blood supply.
    • Imaging: early stress reactions are best seen on MRI (T2-weighted images with high signal intensity in the navicular, indicating edema/inflammation).
    • Treatment: immobilization is the first line; prolonged immobilization can be necessary; some cases may require surgical fixation to improve healing and outcomes; central avascularity makes nonunion more likely.
    • Central third/navicular blood supply is poor (watershed area), increasing nonunion risk; the fibrous/cartilaginous tissue around a navicular fracture may fail to heal without adequate stabilization.
  • Jones fracture and surrounding anatomy
    • Jones fracture near the base of the fifth metatarsal has its own set of treatment considerations; in athletes, some fractures require surgical fixation for rapid return to sport.
  • Cuboid pathology and cuboid syndrome
    • Cuboid syndrome presents with diffuse lateral foot pain, lateral midfoot pain, and sometimes sinus tarsi symptoms; may be misdiagnosed as a lateral ankle sprain.
    • Common associated conditions: peroneus longus tendon pathology, peroneal groove pain, stress fractures around the cuboid, calcaneal fracture, anterior process fracture, and coalition disorders.
    • Clinical tests for cuboid syndrome include the cuboid whip test (to realign the cuboid), cuboid squeeze test, and maneuvers to provoke or reduce displacement; the whip test involves dorsum of the foot being cupped, thumbs placed plantar-medially, knee flexed, ankle at 90 degrees, and a sudden jerking motion to push the cuboid back into place.
    • Management: relocation of the cuboid (whip test) and supportive therapy; imaging may be negative after relocation, hence clinical diagnosis is important.
  • Plantar fibroma and plantar fascia pathology
    • Presentation: a medial plantar mass, often with a mass that is fully movable and transilluminates less light (ganglion cyst-like features; plantar fibromas are non-cystic but can mimic).
    • Diagnostic steps: start with X-ray to rule out bony causes; if negative or soft tissue etiology suspected, MRI or ultrasound is used to characterize tissue.
    • Conservative management: NSAIDs, topical diclofenac, corticosteroid injections (injections carry risks and are used selectively), verapamil (calcium channel blocker) or similar agents for fibromas; sometimes topical agents or infiltration therapies may help.
    • Surgical management: fasciectomy (removal of plantar fascia) to reduce recurrence risk; complete fascia removal reduces the chance of recurrence but alters windlass mechanism and arch height.
    • Alternatives: some clinicians perform a partial fasciectomy or other targeted excisions depending on lesion engagement with the fascia.
  • Ganglion cyst management and recurrence risk
    • Clinical scenario: a painful bump on the top of the foot that transilluminates; differential includes ganglion cyst.
    • Diagnostic approach: imaging (MRI or ultrasound) to confirm cyst and assess contents; if imaging confirms a ganglion, aspiration with analysis of aspirate is performed; sometimes corticosteroid injection follows aspiration.
    • Recurrence risk: ganglion cysts commonly recur after aspiration; recurrence likelihood is high even with surgical excision; removing the stalk may reduce recurrence but complete excision can be technically challenging and may cause stump neuropathies.
    • Practical approach: start with imaging; aspirate with ultrasound guidance when feasible; counsel patients about recurrence risk and discuss possible surgical excision if recurrent or symptomatic.
  • Clinical examination and exam prep themes
    • Systematic approach: always document HPI, ROS, past medical history, medications, and imaging results; perform a thorough vascular and neurological exam when foot and ankle pathology is suspected.
    • Physical exam maneuvers mentioned: piano-key test, gap sign, pronation-abduction test; JAXS (likely Jack’s test) for reducibility of flatfoot with dorsiflexion of the hallux and windlass mechanism; Navicular and midfoot assessment via JAXS (Jack’s test) and Huffshire/Hubscher maneuvers for arch assessment; too-many-toes sign in flexible flatfoot; windlass mechanism as a diagnostic sign for arch function; Dorsiflexion of the hallux to trigger windlass (Jack’s test).
    • High-yield exam topics include plantar fascia pathology, Charcot staging, Lisfranc injuries, navicular and Jones fractures, cuboid syndrome, cuboid whip test, PTTD evaluation, and ganglion cyst management.
    • Always correlate physical exam with imaging and labs; ensure proper documentation of findings and test results; prepare for board-style questions on stage-based Charcot, imaging hallmarks, and treatment algorithms.

Common Differential Diagnoses to Remember (quick cheatsheet)

  • Charcot foot in diabetics: unilateral red, hot, swollen foot; consider DVT, cellulitis, osteomyelitis, gout; CBC with differential to assess neutrophilia in infection; MRI for early Charcot when X-ray is negative (Stage 0).
  • Lisfranc injury: base of the second metatarsal pain, high suspicion with midfoot tenderness; CT or MRI if X-ray is inconclusive.
  • Navicular stress fracture: high suspicion in young athletes with medial foot pain and negative X-rays; MRI T2 shows high signal in navicular; treat with immobilization; consider surgery if nonunion risk is high.
  • Cuboid syndrome: lateral foot pain; cuboid whip test and other maneuvers; differential includes cuboid fracture, ligament injuries near the cuboid, peroneal tendon pathology.
  • Plantar fibroma: medial plantar mass; MRI/ultrasound to characterize; fasciectomy if conservative measures fail.
  • Ganglion cyst: dorsal/plantar foot cyst; high recurrence after aspiration; surgical excision recommended if recurrence or symptomatic.
  • Osteoarthritis signs: osteophytes, asymmetric joint-space narrowing, subchondral sclerosis, cyst formation; management ranges from NSAIDs and orthotics to fusion or, in select joints, replacement.

Quick math and numeric references (LaTeX-formatted)

  • Punch sizes: 2\,\mathrm{mm} and 3\,\mathrm{mm}
  • Time windows: 8\ \text{hours} fixation, 24\ \text{hours} in fluid before processing, 2\ \text{weeks} for oncology referrals when cancer is suspected
  • Population/statistics (as stated in the transcript): 20\ \text{malignant soft tissue tumors per million US residents}
  • Common biopsy depths and gauge references: \text{18G} aspiration needle; punch sizes 2\,\mathrm{mm} or 3\,\mathrm{mm}
  • Biopsy procedures often involve careful depth planning (proximal matrix vs distal matrix) to protect nail structures; explicit measurements not given beyond punch sizes, but depth is discussed qualitatively (deep vs shallow)
  • Imaging and pathology timing: fixation for at least 8\ \text{hours}; processing within 24\ \text{hours}; samples stored in fixative, then moved to cryo, with precise lab-handling times depending on facility policies

Summary takeaways for exams

  • Always correlate clinical exam findings with imaging and pathology; do not rely on a single modality for diagnosis.
  • For suspected malignancy, expedite workup (the 2\text{ weeks} rule) and secure tissue with an appropriate biopsy technique.
  • In biopsy practice, know the difference between punch biopsy, incisional biopsy, and excisional biopsy; choose the approach that yields representative tissue with clear margins while minimizing damage (e.g., nail apparatus in toe lesions).
  • Be fluent in Charcot staging and the off-loading treatment paradigm; remember that the gold-standard for Charcot is a full-time off-loading device (TCC) when appropriate.
  • For common foot/ankle issues: memorize the high-yield tests (piano-key test, gap sign, windlass/Jack’s test), the typical imaging hallmarks of arthritis, and the common treatment ladders for each condition.
  • When dealing with soft-tissue masses: start with imaging, confirm diagnosis, use aspiration cautiously, and discuss recurrence risks with patients; surgical excision has lower recurrence for some lesions but carries its own risks.
  • Always document consent, indications, and the clinical rationale for chosen procedures; be mindful of coding and billing implications in biopsy and specimen handling.