Atypical adenomatous hyperplasia (AAH), one of the most frequently encountered mimics of prostate adenocarcinoma, was originally described by McNeal in the 1960s. Formal recognition of the morphologic criteria supporting the diagnosis of this entity was not established until 1993. These criteria allowed the differentiation of AAH from well-differentiated prostatic adenocarcinoma.

描述：Atypical Adenomatous Hyperplasia

(A) Atypical adenomatous hyperplasia. This focus in a needle biopsy shows clustered acini  of variable size, and containing basal cells. (B) Atypical adenomatous hyperplasia. The clustered acini  again show variable size, benign luminal cells, and occasional basal cells, the presence confirmed in  Figure 12C with the basal cell–specific immunostain. (C) Atypical adenomatous hyperplasia. The basal  cell–specific immunostain 34BE12 (MA903) identifies the reduced numbers of basal cells. (D) Atypical  adenomatous hyperplasia. An extensive area of crowded acini of variable size and configuration.

AAH was defined as a “localized proliferation of small glands within the prostate that may be mistaken for carcinoma.” The acini tend to be closely packed, preponderantly small, and lined by uniform cuboidal or columnar cells with clear cytoplasm . The nuclei are not enlarged and nucleoli are generally small. Only uncommonly will a prominent nucleolus be identified. The periphery of the focus shows an expansile edge with only minimal foci of stromal invasion present. Basal cells are present and can usually be detected in routine stained slides. Basal cell–specific immunostains disclose a discontinuous basal cell population in the acini of AAH. Corpora amylacea is common, and crystalloids are reported in 40% of cases.

非典型腺瘤样增生被定义为：前列腺内小腺体的局部增生，可误认为癌；腺泡排列紧密，内衬立方或柱状细胞，细胞体积小，胞浆透明。细胞核无增大，核仁小。明显核仁的情况不常见。病灶外周呈膨胀性边缘，仅见小灶向间质内浸润生长。通常常规染色切片中可见基底细胞存在。在非典型腺瘤样增生中，基底细胞特异性免疫染色可见不连续性的基底细胞存在。淀粉样体常见，类晶体被报道见于40%的病例。

There is topographic proximity of the foci of AAH with nodular hyperplasia, best appreciated in prostate whole-mount sections. These prostate sections demonstrate the preponderance of AAH clusters within the transition zone and the frequent multifocality of the lesion. The frequency of identification of AAH is highest in prostatectomy specimens (23%), intermediate in TURP specimens, and lowest in needle biopsies (1%) that sample the peripheral zone. In all specimens AAH is an incidental microscopic finding; however, Humphrey and associates reported one mass formative example of AAH in a suprapubic prostatectomy.

The differentiation of AAH from well-differentiated prostatic adenocarcinoma is the most clinically important concern with this lesion. The histologic criteria, applied in aggregate, supplemented with basal cell–specific immunohistochemical stains outlined in the preceding text will identify AAH foci and exclude adenocarcinoma. Problematic cases are associated with large volume foci in needle biopsies, and with examples that show focal immunostaining with AMACR (P504S). This immunostain, characteristically positive in prostate adenocarcinoma, has been reported focally positive in 10%, and diffusely positive in an additional 8% of AAH cases. With the diagnostic criteria established allowing differentiation from prostatic adenocarcinoma, atypical small acinar proliferation (ASAP), and HGPIN, attention was then devoted to the possible malignant potential of AAH. In summary, this remains unsettled, but currently no substantial evidence has been produced to support a premalignant role for AAH. Chromosomal changes are infrequent in AAH, and, when identified, show no similarities with those found in carcinomas from the same specimens. The results of cell kinetic studies are mixed, two studies showing lower proliferative rates in AAH than in prostate adenocarcinoma, and one study reporting a similar labeling index with Ki67 and MIB-1.

与非典型腺瘤样增生相关的重要的临床意义是与高分化前列腺腺癌进行鉴别。

有问题的病例是在针穿活检中见到体积较大的腺瘤样增生和局部免疫染色AMACR (P504S)阳性。

据报道，这一前列腺癌的P504S特征性免疫染色，10%非典型腺瘤样增生的病例局部阳性，8%的弥漫阳性。

根据其诊断标准可以与前列腺癌、非典型小腺泡增生ASAP和HGPIN相鉴别。