This dermatopathology case presentation details the diagnosis and microscopic features of an unusually large, ulcerated, fungating nodule presenting on the fourth toe. The primary diagnosis is Pyogenic Granuloma (PG), also known as Lobular Capillary Hemangioma. The video explores the key microscopic identifiers of PG, including its characteristic lobular architecture, plump endothelial cells, and the presence of pericytes, emphasizing that mitotic activity is a normal reactive feature in this benign lesion. Immunostains (CD31, CD34, and Actin) are demonstrated to confirm the vascular nature and cellular composition. Furthermore, the video highlights a rare "bonus finding": the presence of Extramedullary Hematopoiesis (EMH) near the base of the lesion, an extremely uncommon co-occurrence in cutaneous PGs.
Pathology Review of a Giant Pyogenic Granuloma
0:13 Clinical Presentation & Diagnosis: The case involves a large, ulcerated, fungating nodule on the fourth toe. The final diagnosis is Pyogenic Granuloma (PG) or Lobular Capillary Hemangioma, noted by the presenter as one of the largest he has ever seen.
1:17 Treatment and Recurrence: The lesion was definitively removed by a surgeon via excision (rather than shave), which is favored because it allows for cauterization of feeder vessels, minimizing the high risk of recurrence typical of PGs.
1:42 Key Microscopic Pattern: The PG is pedunculated and exhibits distinct lobular architecture, where clusters of capillaries are organized around central vessels. This lobularity is a crucial feature supporting a benign vascular process.
2:34 Cellular Details: The vessels contain plump endothelial cells and numerous cells in the interstitium, primarily pericytes (modified smooth muscle cells that are actin-positive).
3:00 Differential Diagnosis: If many neutrophils are seen in the middle of a PG, the differential diagnosis should include Bacillary Angiomatosis.
4:01 Plump Endothelial Cells and Mitoses: Endothelial cells may appear plump, and mitotic activity is a normal feature of PGs due to active growth and inflammation. Mitoses and large cells alone should not cause concern for malignancy, but marked pleomorphism or hyperchromatic nuclei warrant careful evaluation.
4:55 Management of Doubtful Cases: Due to the difficulty in differentiating benign vascular tumors from malignancy (like angiosarcoma) without ancillary stains, any doubtful or concerning cases (especially if the base is not fully excised) require close clinical follow-up or further excision.
CD31 (Endothelial Marker): Provides sharp, membranous/cytoplasmic staining, enhancing visualization of the lobular pattern and individual vessel spaces.
CD34: Also stains vessels but is less specific as it stains dermal dendritic cells/fibroblasts strongly (positive in normal dermis and scar tissue), making it generally less helpful for PG architecture than CD31.
9:37 Actin Stain: Stains the pericytes surrounding the vessels. The presence of a clear layer of actin-positive pericytes surrounding the vessels is typical of benign vascular lesions.
10:48 Bonus Finding: Extramedullary Hematopoiesis (EMH): Near the base of the PG, clustered cells of varying size with perfectly round, hyperchromatic nuclei were identified as erythrocyte precursors and myeloid precursors (developing neutrophils), indicative of EMH. This is a rare finding in the skin, noted as the second time the presenter has seen it specifically within a PG.