The basic structural unit of the female breast is a lobule, which consists of a varying number of acini. In lobular hyperplasia there is an increase in the number of acini within the lobules. An average of 78.2 acini has been described in hyperplastic lobules, in comparison to 29.6 acini in lobules of normal women aged 20–40 years [1
]. Besides lobular hyperplasia, sclerosis of the intralobular and interlobular stroma characterizes the entity of "sclerosing lobular hyperplasia" This entity has also been called fibroadenomatosis, fibroadenomatoid mastopathy, or fibroadenomatoid hyperplasia [1
Sclerosing lobular hyperplasia is an infrequently encountered benign proliferative lesion of the breast. It was first described in 1984 by Kovi et al
. and is diagnosed in 3–7% of benign breast biopsies [1
]. Sclerosing lobular hyperplasia most commonly occurs between the ages of 14 and 46 years [1
]. It usually presents as a discrete, palpable, and painless mass in the upper outer quadrant of the breast. Mammography usually reveals a lobular or oval, well-circumscribed mass with echogenic septa that correspond to interlobular sclerosis. Microcalcifications may be seen occasionally, especially in older women. These calcifications may be present in irregular clusters and as granular suspicious lesions. However, distinguishing sclerosing lobular hyperplasia from fibroadenoma on radiologic investigations is difficult in most cases and probably not warranted either, as both lesions are benign and require similar clinical management [5
Fine-needle aspiration cytology findings have been previously reported in two cases of sclerosing lobular hyperplasia [3
]. Both reports emphasized the presence of ductal epithelial cells in monolayered sheets and of round acinar clusters in a clean background devoid of stromal fragments and with only a few bare nuclei. The cytology findings in our case were similar to those described previously, in the lack of elongated and branched tubular fragments. However, unlike the previously described cases, we saw a few scattered stromal fragments and a fair number of bare nuclei. The sclerosed stroma may make fine-needle aspiration a difficult task and also account for the relative paucity of stromal fragments. However, a complete absence of stromal fragments and rarity of bare nuclei are not consistent features of sclerosing lobular hyperplasia and may not be relied upon to distinguish it from fibroadenoma; a reliable distinction requires histologic examination of the architecture of the two lesions.
Grossly, sclerosing lobular hyperplasia is composed of firm, nodular, tan-white tissue. Histologically, there are enlarged lobules with increased numbers of acini. The intralobular stroma is collagenized with loss of stromal mucopolysaccharides, and there is variable sclerosis of the interlobular stroma [1
]. Focally, there may be pseudoangiomatous changes in the sclerosed stroma [8
]. The lobular acini and ducts have distinct single-layered epithelial and myoepithelial components. Secretory activity is not prominent.
Other palpable breast masses in adolescents include fibroadenoma, juvenile papillomatosis, juvenile hypertrophy, and tubular adenoma. Like sclerosing lobular hyperplasia, fibroadenoma is usually a well-defined, firm to rubbery mass. Histologically, sclerosing lobular hyperplasia is distinguished from fibroadenoma by preservation of the acinar architecture, despite the hyperplastic appearance caused by an increased number of acini per lobule and increased collagenized intralobular and interlobular stroma.
Fibroadenomas, on the other hand, clearly differ from normal acinar architecture with their irregular proliferating elongated and distorted ducts and loose cellular stroma [2
]. Sclerosing lobular hyperplasia does appear to be closely related to fibroadenoma. Microscopic fibroadenomas have been described in some sections from sclerosing lobular hyperplasia and sclerosing lobular hyperplasia may occur in the breast tissue surrounding fibroadenomas [1
]. The natural course of sclerosing lobular hyperplasia is not known. However, till date no association with or natural progression towards malignancy has been reported. Excision of the lesion is considered adequate therapy. Recurrences have not been documented [6
In summary, we have described cytologic and histologic features of a case of sclerosing lobular hyperplasia of breast in an adolescent girl. In particular, we wish to emphasize that the presence of stromal fragments in fine-needle aspiration smears from a breast mass does not exclude the diagnosis of sclerosing lobular hyperplasia. Moreover, a "mistaken" diagnosis of fibroadenoma in such cases is of no clinical significance since the two lesions have similar clinical behavior.