A 34-year-old female presents with a small bluish lesion under the nail of her right index finger. The lesion is extremely tender to touch. If the lesion is a tumor, its cells of origin are most likely to have which of the following functions:

Question

A 34-year-old female presents with a small bluish lesion under the nail of her right index finger.  The lesion is extremely tender to touch.  If the lesion is a tumor, its cells of origin are most likely to have which of the following functions:

Quizplus · Accepted Answer

A bluish neoplasm occurring underneath the nail bed may be either a glomus tumor (glomangioma) or a subungual melanoma. Both are rare diagnoses. Melanomas are composed of melanocytes, which have the function of pigmentation. Because 'pigmentation' is not among the answer choices, glomus tumor is the most likely diagnosis. A glomangioma is a tumor of the modified smooth muscle cells of a glomus body. Glomus bodies are numerous small, encapsulated neurovascular organs found in the dermis of the nail bed, the pads of the fingers and toes, and the ears. Each glomus body is composed of an afferent arteriole connected to a richly innervated, muscular arteriovenous anastomosis, which is then connected to an efferent vein. Modified smooth muscle cells are arranged in layers around these vascular channels. The role of the glomus body is to shunt blood away from the skin surface in cold temperatures in order to prevent heat loss, and to direct blood flow to the skin surface in hot environments to facilitate the dissipation of heat. (Choice A) Extremity receptors responsible for proprioception include muscle spindles, Golgi tendon organs, Pacinian corpuscles, and cutaneous touch receptors (including Meissner's corpuscles, Merkel's disks, and free nerve endings). A tumor of any component of these structures (e.g. neurons, connective tissue cells) would not have a bluish coloration. (Choice B) Light touch is mediated by cutaneous mechanoreceptors, which may be encapsulated or free nerve endings. A tumor of these structures would not have a blue hue. (Choice D) A lymphangioma is a tumor of the cells involved in lymphatic drainage. These benign lymphatic neoplasms are analogous to vascular hemangiomas. Lymphangiomas tend to occur subepidermally, in the head, neck, and axilla. They consist of networks of endothelium-lined lymph spaces. Because they do not contain pigmented cells or red blood cells, lymphangiomas would be unlikely to have a bluish appearance. (Choice E) A tumor of antigen-processing cells would be either a histiocytosis or a lymphoma. When there is cutaneous involvement in Langerhans cell histiocytosis, patients present with erythematous papules, nodules, and/or scaling plaques. B-cell lymphomas very rarely involve the skin. (Choice F) The basal epidermal cells of the nail matrix are responsible for nail growth. Tumors originating from the epidermis include squamous cell carcinomas (SCC) and basal cell carcinomas (BCC). SCC does not involve pigmented cells. Although BCC may involve pigmented cells, the majority of these lesions (85%) appear on the head and neck; BCC rarely affects the dorsum of the hands. Educational Objective: A benign glomus tumor (glomangioma) can produce a very tender, small (a few millimeters in diameter), red-blue lesion under the nail bed. This type of tumor originates from the modified smooth muscle cells that control the thermoregulatory functions of dermal glomus bodies.

A 34-Year-Old Female Presents with a Small Bluish Lesion Under