Triple Negative, Basal Cell Type and EGFR Positive Invasive Breast Carcinoma in Kuwaiti and British Patients

To the Editor: Geographic and ethnic variation in the incidence of various types of breast carcinoma are known to exist. We were therefore interested in finding out whether or not there are differences in the incidence of triple negative breast carcinoma and epidermal growth factor receptor (EGFR) positive tumors between patients from a Middle Eastern Country as compared with a Western Country, as this might have implications concerning health planning strategies. Eighty eight patients with invasive breast carcinoma were studied. These included 38 consecutive patients from The University of Kuwait Hospital, including one with bilateral tumors, and 50 consecutive patients from Charing Cross Hospital, London (CX). For each tumor new 5 l-thick paraffin sections were cut and stained for estrogen receptor (ER) (Novocastra, concentration 1:200), progesterone receptors (PgR) (Launch Diagnostics, 1:200), HER2 (Dako, 1:200), cytokeratin 5 ⁄ 6 (Dako, 1:200), and EGFR (Novocastra, 1:200), using standard avidin–biotin immunoperoxidase technique. Because of insufficient tumor tissue in the paraffin blocks of some cases, a few cases were stained for a limited number of these antibodies. For ER and PgR, the histochemical scoring assessment system was used (1), where the percentage of stained tumor cells was multiplied by a factor reflecting the intensity of staining (1 for weak, 2 for moderate, and 3 for strong staining). The results could thus range from 0 (no positively stained tumor cells) to 300 (strong staining of 100% of tumor cells). A minimum score of 30 is needed to consider the case positive. For HER2 and EGFR, a case is considered positive if more than 10% of tumor cells showed strong membrane staining. For cytokeratin 5 ⁄ 6, strong cytoplasmic staining of 10% of tumor cells at least was required to consider the case positive. For statistical comparison, Fisher’s exact test was used. The age of the Kuwaiti patients ranged between 30–70 years with a mean of 50.4. For CX patients the range was 31–79 and the mean 57.7 years. In particular, 16 (42%) out of the 38 Kuwaiti patients were under the age of 50, compared with 11 ⁄ 50 (22%) CX patients. The Fisher’s p-value is 0.06 which is weakly significant. The incidence of the two main histological types, i.e., invasive ductal (77% for Kuwaitis and 78% for CX) and lobular carcinoma (10% and 12% respectively), was similar in both populations. Each of the two studied cohorts included a single case of mucinous carcinoma and another of metaplastic carcinoma. However, medullary carcinoma was present in three (8%) Kuwaiti patients, (two typical and one atypical with partly infiltrative borders), and in none CX patients; while no tubular carcinomas were seen in Kuwaiti patients compared with three (6%) CX cases. The Kuwaiti patients had a higher incidence of grade III tumors (16 ⁄ 39, 56%), compared with CX patients (12 ⁄ 50, 24%); with a p-value of 0.11. Grade I tumors were less common in Kuwaiti patients (4 ⁄ 39, 10%) than in CX patients (10 ⁄ 50, 20%), but the incidence of grade II tumors was not markedly different (19 ⁄ 39; 49% versus 28 ⁄ 50; 56%, respectively). Axillary lymph node metastasis were present in 22 (59%) out of the 37 Kuwaiti patients who underwent axillary dissection, compared with 20 (40%) out of the 50 CX patients who all had axillary dissection. The Fisher’s p-value is 0.14, which is weakly positive. The incidence of ER and PgR positive tumors was similar in the Kuwaiti and CX populations (79% versus 78% for ER and 45% versus 48% for PgR; respectively), and there was no statistical difference between the incidence of cytokeratin 5 ⁄ 6 (16% versus 15%; Fig. 1) and EGFR (15% versus 12%; Fig. 2) positive tumors. HER2 positivity was higher in Kuwaiti than in CX patients (8 ⁄ 39, 21% versus 4 ⁄ 50, 8% respectively, Fisher’s p-value 0.12). Address correspondence and reprint requests to: Sami Shousha, MD, Department of Histopathology, Charing Cross Hospital, Fulham Palace Road, London W68RF, or e-mail: s.shousha@imperial.ac.uk