"Puffy shirt appearance": Cell crowding at low magnification may represent nevoid melanoma.

Background: Melanoma, particularly nevoid melanoma, can masquerade as benign. Helpful differentiating features include nuclear pleomorphism, atypia, prominent nucleoli, absent maturation, and increased mitotic figures. These can be subtle and easily missed unless carefully sought. Thus, the "puffy shirt appearance" concept was born from a Seinfeld episode in which the namesake character unintentionally agreed to wear a pirate-like puffy shirt. Consequently, he found himself out of place, sporting an outfit with "too much shirt in too little space". Similarly, at low-power, nevoid melanoma appears to have "too many cells in too little space". This is more pronounced and easier to appreciate when there is an associated nevus, where crowded, subtly malignant melanocytes stand out from the evenly distributed, more spaced out benign melanocytes.

Methods: Twelve practicing dermatopathologists familiar with the puffy shirt concept in the context of melanoma were surveyed.

Results: Hundred percent of participants found it most helpful as a triaging tool, prompting additional work up including higher magnification evaluation, additional levels, consultation, and/or immunohistochemistry.

Conclusions: The crowded cells in the "puffy shirt appearance" catch the eye and should provoke a more thorough inspection of the lesion. This sign is not pathognomonic for melanoma, but prompts more careful evaluation and helps prevent misdiagnosis.