Skin nonmelanocytic tumor

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Contributed by Bethany R. Rohr, M.D. and Claire Mazahery, M.D., Ph.D.

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A 30 year old woman presented with a flesh colored papule on the arm. A biopsy was performed. What is the predominant inheritance pattern of the familial form of this entity?

1. Autosomal dominant mutations in keratin 17
2. Autosomal dominant mutations in keratin 18
3. Autosomal recessive mutations in keratin 17
4. Sporadic lesions only

A. Autosomal dominant mutations in keratin 17. The solitary lesion in the question above is steatocystoma simplex. Steatocystoma multiplex can be seen as a sporadic or an autosomal dominant disease presenting with multiple steatocystomas. The heritable form is thought to be due to mutations in keratin 17. Answer D is incorrect because although the patient in the question stem has a single lesion (steatocystoma simplex, which is sporadic), steatocystoma multiplex has identical lesions on histology. Answer C is incorrect because steatocystoma multiplex is an autosomal dominant (not recessive) mutation in keratin 17. Answer B is incorrect because the mutated gene is keratin 17, not keratin 18.

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Reference: Steatocystoma

A 40 year old man presents with a longstanding history of multiple asymptomatic, firm, flesh colored papules across the chest and upper back. He notes several family members with similar skin lesions. A close physical examination revealed thickened nails that he says have been a source of embarrassment since childhood. What adnexal structure is associated with his skin lesions?

1. Apocrine glands
2. Eccrine glands
3. Follicular structures
4. Sebaceous glands

D. Sebaceous glands. The patient's nail changes present since early life are suggestive of pachyonychia congenita, which can co-occur with familial steatocystoma multiplex (keratin 17 mutations present in both diseases), accounting for the skin findings in this patient and his family members. The cysts of steatocystoma multiplex are associated with sebaceous glands. Answers A and B are incorrect because these may be seen in hidrocystoma. Answer C is incorrect because these are found in follicular based cysts (such as pilar cyst, vellus cyst or epidermal inclusion cyst).

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Reference: Steatocystoma