This transcript features a pathology discussion detailing the microscopic identification of a myofibroma. The specimen is characterized by a biphasic appearance, consisting of prominent, colored nodules (described as "cotton candy colored"—pinkish-purplish/lavender) situated among more cellular areas containing characteristic vascular patterns. The nodules are noted for their bland, spindle-to-oval cells arranged in fascicles, sometimes exhibiting a bluish, mixoid, or "pseudo-chondroid" appearance. The intervening areas feature Bland spindle cells compressed between highly prominent, dilated, branching, interconnected vessels, sometimes referred to as "staghorn" or hemangioparasitic vessels. Key diagnostic features include the cells pushing into the vessel lumens. The presenter confirms the diagnosis is a classic myofibroma, notes its usual presentation in babies/children, emphasizes its generally benign and indolent nature (often regressing spontaneously or not recurring post-excision), and mentions the occasional presence of calcification.
Microscopic Diagnosis of a Classic Myofibroma
0:00:08 Appearance: Specimen described as "cotton candy colored" (pinkish-purplish/lavender) and presenting as multi-nodular masses.
0:00:38 Biphasic Structure: The lesion consists of two main components: oriented nodules and intervening cellular material.
0:01:14 Nodule Characteristics: Nodules contain nondescript, slightly plump, spindle to oval cells arranged in fascicles, often compressed between dilated vascular spaces. These areas are described as having a bluish, mixoid, or "pseudo-chondroid" appearance (0:03:39).
0:01:40 Vascular Pattern: The intervening areas feature highly prominent, dilated, branching, interconnected vessels, classically termed "staghorn" or hemangioparasitic vessels.
0:02:19 Key Clue: The neoplastic cells are observed bulging or growing into the lumens of these vessels.
0:02:40 Diagnosis Confirmed: The diagnosis is a myofibroma. These cells are myofibroblastic (actin positive, usually desmin negative).
0:04:09 Patient Demographics: Classically seen in babies and children, though they can appear in older adults.
0:04:12 Clinical Course: Lesions are generally totally benign and indolent; they may regress spontaneously, and recurrence after complete excision is uncommon.
0:04:51 Differential Consideration: More cellular variants without clear nodularity can be harder to diagnose microscopically.
0:05:19 Additional Feature: The lesion can sometimes develop focal dystrophic calcifications or metaplastic bone.
0:05:32 Diagnostic Method: The diagnosis is typically made reliably on routine H&E staining without requiring special immunohistochemical stains.