Expression of TdT in Myoepithelial Cells: Investigation in Breasts, Sweat Glands, and Salivary Lesions Emphasizing the Never-Documented Immunohistochemical Findings

Abstract

Background. The expression of terminal deoxynucleotidyl transferase (TdT) in myoepithelial cells (MECs) within the breast was recently incidentally observed in our routine practice. This study aimed to elucidate the expression of TdT in MECs. Methods. TdT immunostaining was performed on 180 mammary, 89 cutaneous, and 94 salivary tissues or lesions. Other myoepithelial markers, including P63, calponin, and SMA as well as double staining for TdT and calponin, were also evaluated in some cases. Selected lesions with basal or myoid differentiation were also included in the investigation. Results. MECs were positive for TdT in mammary lesions that contained MECs (132/135) but negative when they did not contain MECs (45/45). MECs in sweat glands (24/30) and their neoplastic counterparts, including those in hidradenoma papilliferum (2/9), spiradenoma (6/6), and cutaneous mixed tumor (9/9), showed weak to moderate TdT positivity. MECs were variably immunolabeled for TdT in salivary or salivary gland–type tumors with myoepithelial differentiation (pleomorphic adenoma, 24/25; basal cell adenoma, 6/7; adenoid cystic carcinoma, 7/7; Warthin tumor, 0/6; mucoepidermoid carcinoma, 0/8; acinic cell carcinoma, 0/4), but MECs in normal salivary gland barely stained for TdT (30/32). Conclusions. Our findings indicate that TdT may be eligible as an additional auxiliary immunohistochemical marker as P63, but not a surrogate, to identify the MECs in the breast with limited cross-reactivity, particularly in lesions with a prominent proportion of MECs. Positivity for TdT, along with other relevant markers, in a subset of sweat gland lesions and salivary tumors may contribute to their diagnosis.

Terminal Deoxynucleotidyl Transferase Commonly Expresses in Germ Cell Tumors: Evaluation on a Large Series from Multiple Centers

“…21 Four-micron-thick sections were taken from 10% formalin-fixed and paraffin-embedded tissue blocks, as described previously in literature. 15,22 Then the immunohistochemical staining was performed using a Dako automated immunohistochemistry system (Dako, Carpinteria, CA, US) according to the manufacturer's protocol. 23 All of the primary antibodies were commercially available including TdT (EP266, prediluted; Dako, Carpinteria, CA, US), PLAP (EP194, 1:100; ZSGB-Bio, Beijing, China), OCT4 (N1NK, prediluted; Dako, Carpinteria, CA, US), SALL4 (6E3, 1:50; ZSGB-Bio, Beijing, China), CD117 (YR145, prediluted, MXB Biotech, Fuzhou, Fujian, China) and D2-40 (D2-40, prediluted, Dako, Carpinteria, CA, US).…”

“…Appropriate positive (thymus) and negative controls (fibroblasts) were used. 15 For some unsatisfactory staining results due to long-term archiving, we selected another representative tissue block and optimized antigen retrieval and coloration time; another Bond automated immunohistochemistry system (Leica Microsystems, Wetzlar, Germany) was also used. Immunoreactivity was evaluated semiquantitatively according to the percentage of immunoreactive tumor cells: 0, no staining; 1+, fewer than 30% positive; 2+, 31% to 60% positive; 3+, 61-90% positive; 4+, more than 90% positive.…”

“…[9][10][11] However, some nonlymphoid tumors tagged with TdT exist, including 73% of Merkel cell carcinomas, myoepithelial cells, few small cell lung carcinomas, and normal and neoplastic sebaceous cells. [12][13][14][15][16] Recently, we encountered a case of mediastinal seminoma demonstrating diffusely TdT-positive nuclei. Alexander Brobeil et al reported that seminoma (10/10) and germ cell neoplasia in situ (GCINS) (2/2) were positive for TdT.…”

“…Primary lymphomas account for 1% to 9% of testicular neoplasms and 1.5% of ovarian neoplasms. 28,29 Although the most common testicular or ovarian lymphomas (eg, diffuse large B cell lymphoma, DLBCL) usually develop in the elderly, primary lymphoma or secondary to systemic lymphohematopoietic malignancies in children or adolescents were also reported, such as Burkitt lymphoma, lymphoblastic lymphoma, DLBCL, and anaplastic large B cell lymphoma. 28,[30][31][32][33][34] Histologically, the seminomas or dysgerminomas and solid ECs can display sheets of tumor cells with pronounced nucleoli that may mimic the lymphomas.…”

Diagnostically misleading aberrant terminal deoxynucleotidyl transferase expression in germ cell tumors

“…In the former, this phenomenon may occur due to the differentiation programming prior to apoptosis initiated by the holocrine secretion mode [16]. On the other hand, no DNTT mRNA was detected in myoepithelial cells [17]; thus, cross-reactivity with another antigen should be considered (similarly to GCT).…”