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Presented by Justin A. Bishop, M.D. and prepared by Matthew Olson, M.D.
Case 3: 45 M with a “parotid lump.”
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1. Question
Week 502: Case 3
45 M with a “parotid lump.”images/1Alex/10_31_3_1.jpg
images/1Alex/10_31_3_2.jpg
images/1Alex/10_31_3_3.jpgCorrect
Answer: Spindle cell lipoma
Histology: The tumor consists of a spindle cell proliferation without any parotid tissue (despite being designated a partoid lump). The spindle cells are bland, and admixed with a minor component of adipose tissue. A striking feature is the bundles of ropy collagen between the tumor cells. Mast cells are easily found. The tumor was strongly positive for CD34 and negative for S100.
Discussion: Spindle cell lipoma (SCL) is an unusual variant of lipoma that is typically encountered in the subcutaneous tissue of the posterior neck, back, and shoulder of men 45-60 years old. In SCL, the proportion of spindle cells and mature fat cells varies from tumor to tumor, and SCL can be difficult to recognize when it is dominated by spindle cells. The collagen characteristic for SCL can also be seen in neurofibromas, but SCL is consistently positive for CD34 and negative for S100. The histologic features including CD34 positivity of SCL overlap considerably with those of solitary fibrous tumor, so much so that some consider the tumors to be in the same “family” along with mammary-type myofibroblastoma. The absence of staghorn (hemangiopericytoma-like) vessels supports the diagnosis of SCL over SFT. SCL is entirely benign and generally does not recur after excision.
Incorrect
Answer: Spindle cell lipoma
Histology: The tumor consists of a spindle cell proliferation without any parotid tissue (despite being designated a partoid lump). The spindle cells are bland, and admixed with a minor component of adipose tissue. A striking feature is the bundles of ropy collagen between the tumor cells. Mast cells are easily found. The tumor was strongly positive for CD34 and negative for S100.
Discussion: Spindle cell lipoma (SCL) is an unusual variant of lipoma that is typically encountered in the subcutaneous tissue of the posterior neck, back, and shoulder of men 45-60 years old. In SCL, the proportion of spindle cells and mature fat cells varies from tumor to tumor, and SCL can be difficult to recognize when it is dominated by spindle cells. The collagen characteristic for SCL can also be seen in neurofibromas, but SCL is consistently positive for CD34 and negative for S100. The histologic features including CD34 positivity of SCL overlap considerably with those of solitary fibrous tumor, so much so that some consider the tumors to be in the same “family” along with mammary-type myofibroblastoma. The absence of staghorn (hemangiopericytoma-like) vessels supports the diagnosis of SCL over SFT. SCL is entirely benign and generally does not recur after excision.
