The diagnosis is made either by testing of the fumarate hydratase activity in cultured skin fibroblasts or lymphoblastoid<unk> s and demonstrating reduced activity (≤60%) or by molecular genetic testing. Special histologic features of fibroids may allow an early diagnosis in absence of other symptoms. Histology The skin lesions may be difficult to diagnose clinically but a punch biopsy will usually reveal a Grenz zone separating the tumour from the overlying skin. Histological examination shows dense dermal nodules composed of elongated<unk> s with abundant eosinophilic cytoplasm arranged in fascicles (spindle<unk> s). The nuclei are uniform, blunt-ended and cigar-shaped with only occasional mitoses. Special stains that may be of use in the diagnosis include Masson's trichrome, Van Gieson's stain and phosphotungstic acid–haematoxylin. The renal<unk>  carcinomas have prominent eosinophilic nucleoli surrounded by a clear halo. Differential diagnosis Differential diagnosis of this condition includes the Birt-Hogg-Dubé syndrome and tuberous sclerosis. As the skin lesions are typically painful, it is also often necessary to exclude other painful tumors of the skin (including blue rubber bleb nevus, leiomyoma, eccrine spiradenoma, neuroma, dermatofibroma, angiolipoma, neurilemmoma, endometrioma, glomus tumor and granular<unk>  tumor; the mnemonic "BLEND-AN-EGG" may be helpful). Other skin lesions that may need to be considered include cylindroma, lipoma, poroma and trichoepithelioma; these tend to be painless and have other useful distinguishing features.
Hereditary leiomyomatosis and renal cell cancer syndrome
Menke-Hennekam syndrome
Hereditary leiomyomatosis and renal cell carcinoma
Fryns syndrome
Heerfordt syndrome
Serrated polyposis syndrome
Hereditary breast–ovarian cancer syndrome
Ehlers–Danlos syndromes