Q: What is the clinical presentation of the trichilemmal cysts and proliferating trichilemmal cysts?
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A: Trichilemmal cysts and proliferating trichilemmal cysts are usually asymptomatic and may manifest as lobulated masses within the scalp. Alopecia, ulceration, and infection on the local of the tumor may occur. Occasionally clinical presentation will be with superimposed infection or rupture. Malignant transformation is very uncommon. The more aggressive behavior is more common in tumors located out of the scalp, tumors larger than 5 cm, with atypia, and mitotic activity. Some cases of proliferating trichilemmal cysts may be associated with Cowden syndrome.
Q: When are imaging studies useful for the diagnosis of trichilemmal cysts/proliferating trichilemmal cyst?
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A: The diagnosis of trichilemmal cysts and proliferating trichilemmal cysts are mainly on clinical signs and symptoms. Ultrasonography, CT scanning, and MRI are imaging tests occasionally useful in the investigation of these lesions, mainly to exclude other differentials and verify to the extent of the lesion, bone invasion, and the involvement of the underlying central nervous system. CT is the best tool to monitor bony erosion, whereas MR is more useful to assess soft-tissue infiltration and dural involvement.
Q: Which are the CT appearance of trichilemmal cysts/proliferating trichilemmal cysts?
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A: Trichilemal cysts and Proliferating trichilemmal cysts are usually located within the scalp and appear as multiple or solitary complex subcutaneous solid or cystic nodules. On CT, trichilemmal cysts appear as well-defined, hypodense masses with multifocal, punctate, coarse, or curvilinear calcifications. They usually do not enhance. The cystic components may contain high-density proteinaceous material, which sometimes layers dependently. Ring-like patterns of mineralization may occur. Proliferating trichilemmal cysts may show foci areas of enhancement. Malignant transformation may occur, with radiographic signs of bone erosion, meninges involvement, dural sinuses invasion. Other findings of malignancy are the enhancement and infiltration of the surrounding soft tissue components.
Q: Which are the MR appearance of trichilemmal cysts/proliferating trichilemmal cysts?
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A: trichilemmal cysts usually show isointense to brain parenchyma on T1-WI, with no enhancement. On T2-WI, there is a heterogeneous high signal, which may be due to calcifications. There may be internal “blooming” on T2*-WI, which suggests calcifications. The underlying skull vault and skin surface are usually not affected, but occasionally atrophy of the overlying skin and superficial ulceration may occur. Proliferating trichilemmal cysts may show enhancement of the walls with variable thickness and mural nodules. Lesions that have undergone malignant change display signs of local invasions, including marginal unsharpness, enhancing soft tissue components, or bony erosion.
Q: How is the treatment of trichilemmal cysts/proliferating trichilemmal cysts?
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A: Trichilemmal cysts/proliferating trichilemmal cysts are occasional incidental subcutaneous nodules finding on routine brain imaging, and even when asymptomatic, it needs surveillance. Surgical removal may be indicated for cosmetics reasons or due to general discomfort caused by the cysts and to prevent the possibility of malignant transformation. Trichilemmal cysts are easily enucleated, but proliferating trichilemmal cysts require wide resection to prevent a recurrence. Sometimes, proliferating trichilemmal cysts with cytological atypia have unknown biological behavior and might recur and need various surgical excisions, and in rare select cases of malignant transformation, radiation therapy and chemotherapy.
Q: Which are the differential diagnosis of trichilemmal cysts and proliferating trichilemmal cysts?
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A: The differential diagnosis of trichilemmal cysts and proliferating trichilemmal cysts is with a dermoid cyst, epidermoid cyst, cutaneous lipoma, pilomatricoma, acne keloidalis nuchae, steatocystoma multiplex, Favre-Racouchot syndrome, trichilemmal carcinoma, and carcinoma (basal/squamous).
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