Pleomorphic Adenoma with a Novel Gene Rearrangement-LINC01606::PLAG1

BACKGROUND

Pleomorphic adenoma is a well-known benign salivary gland neoplasm characterized by the presence of varying proportions of three different components, including bi-layered ducts, myoepithelial cells, and admixed within a chondromyxoid/fibrous stroma.

METHOD

We report an interesting case of an adult male who presented with bleeding from an extensively degenerated parotid gland mass, concerning for a vascular neoplasm versus primary malignant tumor. Microscopically, majority of the viable tumor exhibited diffuse proliferation of spindle to epithelioid cells, with focal areas depicting cribriform glands, ducts, and scant chondromyxoid stroma.

RESULT

Next-generation sequencing (NGS) RNA-based fusion panel analysis identified a gene rearrangement involving the pleomorphic adenoma gene 1 (PLAG1), with a novel, cryptogenic fusion partner known as LINC01606; [LINC01606::PLAG1; inv(8;8)(8q12.1;8q12.1)].

CONCLUSION

To the best of our knowledge, this is the first documented case of a long non-coding RNA (lnc-RNA) serving as a rearrangement partner with the PLAG1 gene. We reviewed the molecular characteristics of this entity and explored the potential role of LINC01606::PLAG1 in the tumorigenesis of pleomorphic adenoma.

Intraoperative Lymph Node Assessment (Touch Preparation Only) for Metastatic Breast Carcinoma in Neoadjuvant and Non-neoadjuvant Settings

CONTEXT.—

Touch preparation (TP) alone is discouraged for intraoperative lymph node (LN) assessment in the neoadjuvant setting (NAS) owing to overall low sensitivity in detecting metastatic breast cancer.

OBJECTIVE.—

To compare the sensitivity, specificity, and negative predictive value of intraoperative LN assessment via TP and examine potential causes of discrepancies along with the clinical, radiologic, and pathologic parameters in the NAS and non-neoadjuvant setting (NNAS).

DESIGN.—

A total of 99 LNs from 47 neoadjuvant patients and 108 LNs from 56 non-neoadjuvant patients were identified. Discordant cases were reviewed retrospectively to reveal the discrepancy reasons. Clinical, radiologic, and pathologic data were obtained from chart review and the pathology CoPath database.

RESULTS.—

The sensitivity, specificity, and negative predictive value of TP in NAS and NNAS were 34.2% versus 37.5%, 100% versus 100%, and 70.9% versus 90.2%, respectively. In NAS, discrepancy reasons were interpretation challenge due to lobular histotype, poor TP quality secondary to therapy-induced histomorphologic changes, and undersampling due to small tumor deposits (≤2 mm); the latter was the major reason in NNAS. More cases with macrometastasis were missed in NAS compared to NNAS (14 of 25 versus 1 of 10). The parameters associated with discrepancy were lobular histotype, histologic grade 2, estrogen receptor positivity, HER2 human epidermal growth factor receptor 2 negativity, multifocality, and pathologic tumor size greater than 10 mm in NAS; and lymphovascular space involvement and pathologic tumor size greater than 20 mm in NNAS.

CONCLUSIONS.—

In NAS, intraoperative TP alone should be used very cautiously owing to a high false-negative rate of macrometastasis, especially for patients with invasive lobular carcinoma and known axillary LN metastasis before neoadjuvant therapy.